Air-cushioning material is commonly used in the manufacturing and packaging industry as an effective packing dunnage to protect packaged products. This particular dunnage product utilizes a flexible plastic sheet laminate which includes a multitude of encapsulated air pockets. Each air pocket acts to cushion an abutting product in a container or package against impact during shipping and handling.
Other commonly used dunnage materials include various shapes of extruded polystyrene plastic, such as hemispherical cup shapes, spiral "s" shapes ("worms"), and tubular pellets Foam rubber, foamed plastics and expanded polyurethane foam material can also be used, as well as rolled-up newspaper and popped popcorn.
Air-cushioning material is generally a preferred packing dunnage over the above-listed alternatives because it is lightweight, can be supplied and dispensed in a controlled manner, i.e., the air-cushioning dunnage can be provided in a supply roll form and applied to the product in sheet form. Furthermore, the air-cushioning material can be wrapped around the product prior to packaging and still provide effective cushioning characteristics over that provided by newspaper, for example. Loose dunnage alternatives such as polystyrene pieces, foam rubber pieces and popped popcorn include the disadvantage of being difficult to remove from the package and dispose of once the product is removed. In contrast, the air-cushioning dunnage can be removed as a one-piece sheet and flattened (deflated) and rolled to a compact size for easy disposal or reuse.
Unfortunately, use of air-cushioning material as packing dunnage also includes problems. These problems primarily stem from the availability of the supply of air-cushioning dunnage by a manufacturer or other user. The currently available machines for producing the air-cushioning material are large, heavy machines designed to produce the air-cushioning material in great volumes. These machines are generally owned and operated by companies that produce and sell the dunnage material to product manufacturers which, in turn, use the air-cushioning dunnage to protect their packaged products. The users of the dunnage material become dependent on the dunnage-producing companies and therefore, commonly purchase and store a large quantity to avoid availability problems. The air-cushioning dunnage material is already produced, i.e., filled with encapsulated air pockets prior to storage by the manufacturer, and therefore, requires a large area for storage.
Product manufacturers and other dunnage consumers located in or near a city find difficulty reserving valuable space for storage of dunnage supply. The space requirement is especially difficult to meet on board military and merchant sea going ships which use the dunnage to protect various on-board equipment and packages against damage in rough seas, for example.
Currently available machines for producing the air-cushioning material include complex heat controlling systems for regulating the temperature of various parts (forming and heated rollers) which assist in producing the encapsulated air pockets within the plastic sheet laminate.
The method and apparatus for producing air-cushioning dunnage typically includes two supplies of a heat-sealable plastic sheet which can be heated to a temperature suitable for heat-softening, heat welding or heat-melting, as required during the process. In the prior art process for producing air-cushioning dunnage a first plastic sheet is heat-softened and brought into contact with a forming roller which includes a multiplicity of cavities. Vacuum is applied from within the forming roller to the extent that a pre-softened portion of the sheet is drawn into the cavities, thus forming "open" air-pockets into the sheet. The vacuum is active only along one portion of the forming roller. The forming roller typically used in the prior art process is quite large having a diameter of up to three feet and slowly rotates at a rate less than three RPM. Such large forming rollers allow the manufacturer to precisely control the surface temperature of the roller at various important positions (arc-degree-sections) along the roller's surface, as discussed below. Unfortunately, such precise temperature control cannot be effectively obtained with a smaller, more compact roller using the same temperature control method. The compactness of the prior art machines is limited by the method used to make air-cushioning material.
After the first sheet is formed with "open" air-pockets or bubbles the material enters a region of the forming roller which is heated to a much higher temperature sufficient to heat-weld the plastic to an adjacent second plastic sheet supply which is also heated to the same heat-weld temperature. The second supply of plastic sheet is typically drawn along a heated roller (which has a smooth surface, no cavities). The heated roller is abutted against the forming roller to the extent that the two plastic sheet supplies contact each other, forming a heat-weld. The once "open" air-pockets (bubbles) become "closed" and sealed by the welded second plastic sheet.
Once the weld between the two plastic sheets is made, the formed dunnage, still in contact with the forming roller enters a cooled region of the forming roller which allows the laminate to cool to a more stable temperature so that it can be removed from the forming roller without damage. The plastic sheet laminate including the formed air-pockets leaves the forming roller and is usually further cooled using a remotely located cooling roller. The air-cushioning laminate is then rolled and cut to form dunnage supply rolls which are eventually sold to manufacturers in bulk.
The surface of the prior art forming rollers, as it rotates, is continuously heated and cooled. The temperatures achieved at the various arc-degree locations along the surface are critical if good quality dunnage is to be formed (good quality dunnage includes greatly inflated air bubbles sealed by strong heat-welds around each bubble without any melting deformations or burn spots). The surface of the prior art forming rollers are typically heated with an external electric heating element and cooled centrally with a flow of cooling fluid such as air mist or a liquid coolant. Any heat generated along the roller's surface is immediately drawn towards the cooler center. The prior art method of forming the air-cushioning material does not provide a forming roller that cools the formed thermoplastic sheet just prior to heat-welding. The prior art technique generates a surface heat-weld temperature a few degrees before the point of welding and sealing the air-pockets. The air-pockets formed by this prior art method are therefore, very hot prior to and during the welding procedure. The result is sealed air-pockets that are slightly deflated when finally cooled.
In contrast, the present invention provides an air-cushioning producing machine having a non-heated forming roller which maintains the formed air-pockets, and the air within the "open" pockets at a cool temperature throughout the procedure so that the resulting sealed air-pockets do not deflate as a result of differences between internal and external temperatures.
The use of such prior art air-cushioning machines requires careful temperature control of the forming (and heated) roller. Such temperature control requirements together with the prior method of forming air-cushioning material prevent the use of an air-cushion producing machine which is lightweight, simple, compact and inexpensive to the extent that individual dunnage users can own and operate the machine locally and thereby eliminate the dependence on dunnage producers. Such compact dunnage machines can be easily operated adjacent the packaging operation of a product manufacturer (or user) including use on board ships.
There are a number of patents in the particular field of air-cushioning dunnage production, such as, Australian Pat. No. 160,551, published Oct. 29, 1953, and U.S. Pat. Nos. 3,018,015; 3,142,599; 3,231,454; 3,285,793; 3,349,990; 3,577,305; 3,389,534; 3,523,055; 3,575,781; 3,616,155; 3,785,899; 3,817,803; 3,837,990; 3,837,991; 3,868,056; 4,076,872; and 4,096,306. In addition, U.S. Pat. Nos. 3,416,984 and 3,392,081 show basic construction methods and U.S. Pat. Nos. 4,415,398 and 4,427,474 show plural sheets and/or drum roller apparatus. In general, the prior art apparatus are directed to high-volume production with, as discussed above, the resulting dunnage product sold in bulk (typically in the form of rolls) to product manufacturers and other dunnage consumers. The prior art machines all heat the forming roller in order to weld the film together. In contrast, the present air-cushioning machine is intended for use within the product manufacturing building, in the product packing room, for example. The dunnage produced by the present machine can either be rolled and stored for future high demand periods, or produced and immediately used, directly from the machine to the package, following an as-it-is-needed schedule. In either case, the simplicity of the present apparatus enables interruption of dunnage production and, when required, easy repair of the apparatus.
The prior art apparatus and methods for producing air-cushioning dunnage do not anticipate the forming of dunnage using plies of thermoplastic film having a thickness less than one mil. The present apparatus is capable of producing air-cushioning dunnage material using thermoplastic plies, each being one-half mil in thickness. By being able to use such thinner plies to make the dunnage, the resulting dunnage material is less expensive and lighter. Lightweight packaging dunnage is particularly important where items packed with such dunnage are shipped by air.